Obesity is becoming a growing concern, particularly in the United States, as the number of obese people continues to increase, and more is learned about the negative health effects of obesity. Morbid obesity, in which a person is 100 pounds or more over ideal body weight, in particular poses significant risks for severe health problems. Accordingly, a great deal of attention is being focused on treating obese patients. One method of treating morbid obesity has been to place a restriction device, such as an elongated band, about the upper portion of the stomach. Gastric bands have typically comprised a fluid-filled elastomeric balloon with fixed endpoints that encircles the stomach just inferior to the esophageal-gastric junction to form a small gastric pouch above the band and a reduced stoma opening in the stomach. When fluid is infused into the balloon, the band expands against the stomach creating a food intake restriction or stoma in the stomach. To decrease this restriction, fluid is removed from the band. The effect of the band is to reduce the available stomach volume and thus the amount of food that can be consumed before becoming “full.”
Food restriction devices have also comprised mechanically adjusted bands that similarly encircle the upper portion of the stomach. These bands include any number of resilient materials or gearing devices, as well as drive members, for adjusting the bands. Additionally, gastric bands have been developed that include both hydraulic and mechanical drive elements. It is also known to restrict the available food volume in the stomach cavity by implanting an inflatable elastomeric balloon within the stomach cavity itself. The balloon is filled with a fluid to expand against the stomach walls and, thereby, decrease the available food volume within the stomach.
With each of the above-described food restriction devices, safe, effective treatment requires that the device be regularly monitored and adjusted to vary the degree of restriction applied to the stomach. Traditionally, adjusting a gastric band required a scheduled clinician visit during which a Huber needle and syringe were used to penetrate the patient's skin and add or remove fluid from the balloon via the injection port. More recently, implantable pumps have been developed which enable non-invasive adjustments of the band. An external programmer communicates with the implanted pump using telemetry to control the pump. During a scheduled visit, a physician places a hand-held portion of the programmer near the gastric implant and transmits command signals to the implant. The implant in turn adjusts the band and transmits a response command to the programmer.
Implants such as those described above include electronics which require a power source that is sufficient for the intended function, such as making adjustments to the gastric band. Such devices may be internally powered by a battery or capacitor while others may be powered by an externally coupled power source or passive telemetry system. When coupling externally, the efficiencies between the implant and external device diminish substantially as the distance between them increases. There can also be significant power losses through tissue.
Accordingly, there is a need for methods and devices for charging implanted electronics efficiently through tissue by using external and/or non-invasive techniques. It would also be advantageous for a patient to be able to recharge implants without having to travel to a scheduled clinician visit.